Now it is easier to find duplicates and unverified listings in Google Maps. You can do so via Google Map Maker.

This is documented by Linda Buquet in the Local Search Forums. In short, go to Google Map Maker and conduct your search.

Any results with the green shield is a verified listing, the others are not:

Google did not delete all unverified pages as some expected. Google only deleted or hide what they call “Shell Pages.” Shell Pages are pages are any listing not created by a person AND not claimed will be deleted, according to Google. Pages created by humans will stay, Google told Linda.

This is the example Google gave:

So using Map Maker to find legacy or orphaned pages is still an important aspect of local SEO.

Forum discussion at Local Search Forums.